Is there a list of language/text or else instructions on how to create effects.

Since Wizards does not provide a way to license their data and in order to provide maximum flexibility for third party and custom power definitions, the 4E ruleset attempts to automatically parse as many rolls and effects as possible from the description text using a very large word tree. However, the word tree was built for maximum coverage, but there were some things that could not be captured correctly (either due to Wizards tendency to change wording or due to conflicting word use). I believe that the 4E parsing system works at about 90% as is, so you may need to massage rolls or effects that are not parsed exactly how you would expect.

There is no easy way to portray a complicated effect system such as the one provided by 4E, but this one has grown organically over time to support most use cases. The interface could definitely use some work, and is being tracked on my internal wish list.

For a description of what you see in the power effect controls shown in the character sheet:

• Top button is for "targeting" and can be set to "Self" or "Target". If self specified, then the effect will always be applied to the character. Otherwise, the effect will be applied to the character's targets (if any). If no targets specified, then it will be output to the chat window.
• Bottom button is for "application" and can be set to "All", "Action", "Roll" or "Single". If all specified, then the effect will be applied to all rolls until it expires. If action specified, then the effect will be applied to all rolls in the next action (attack, damage, etc.), and then the whole effect will expire. If roll specified, then the effect will only be applied to a single roll, regardless of how many rolls are requested in the next action; and then the whole effect will expire. If single specified, then each modifier will be applied as applicable, and that component of the roll will expire.
• The text is the "label" of the effect. Over time, this has become a way to specify roll modifiers to be applied automatically, which is what you are figuring out now. The main gist is that each modifier/condition is separated by a semicolon. If a tag is recognized by FG as a modifier/condition tag, then it will be handled as explained in the guide. Otherwise, it is purely informational.
• The duration of the effect comes at the end of the effect window, and can be set to "End", "Start", "End N", "Enc", "Save" or None. If set to none, then effect will not expire automatically. Otherwise, it will expire as specified. The number next to the expiration is the initiative value for Start and End expiration values, or the save modifier for the Save expiration value.

For the specific examples you asked about:

• The bracketed ability tags (i.e. [CON], [-DEX]) only work when applying powers from the character sheet, and are calculated when the effect is applied. If a numeric value also is specified, then the values are added together. These bracketed ability tags have no meaning in the campaign effects list or once applied in the combat tracker.
• There are a view special effect tags that can be used to handle lingering or conditional effects. The AFTER/FAIL tags are used to implement Aftereffect and Failed Save clauses; while the IF/IFT tags are used to determine whether to apply effect depending on the effects or Bloodied status of the source or target of the subsequent rolls.
• There is not a great implementation of half damage on miss yet. The current workaround is to roll damage without targets, right click on the roll result and choose the half option, then drag the result to the creatures missed.
• There is not currently a way to simulate resistance reduction. This has to be adjusted manually for now.
• I'm not sure why you ended up with double semi-colons, but they should have no effect on the behavior of the effect.

Other tidbits:

• Rolls and effects can be dragged from the chat window and dropped on the combat tracker to apply them to a specific combatant. If the combatant is linked to a token on a map, it can also be dropped on that token.
• After dropping combatants in the combat tracker and setting a token, you can drag and drop them on to any image to create a token linked to that combat tracker entry. Tokens dropped directly from token bag are not linked to any records.
• You can drag and drop the faction buttons on the bottom of the combat tracker to an image to add all the tokens of combatants of that faction all at once.

Please let us know if you have more questions.

Regards,
JPG

Thanks for the taking the time- much appreciated, I have read and mostly understood- I feel the need to explain that I am not entirely stupid, I have a couple of university degrees but I am a bit flustered by terms like tag, label et al.

You sir, are a gentleman (if indeed you are a man).

Cheers goonalan

I'm trying to create an effect for a Warlord's Tactical Presence, basically half INT Mod to the next attack roll, I can't make it work; I've tried-

TRGT
ROLL
ATK: 1/2x[INT]

I've tried the 1/2 in the brackets, before and after the brackets, in round brackets. I've even tried it as 0.5; and with or without the 'x'- can it be done, if so then how?

goonalan

You can use [-STR] (negative), [HSTR] (half), [2STR] (double); and the valid attributes are STR, DEX, CON, INT, WIS, CHA, LVL

Cheers,
JPG