Will you add the Steam workshop support?
We already have the support. Please see these Wiki pages:
Will you add the editor to MAC OS X, Linux or consoles?
Not in it's current form - the editor is way too complex and Windows dependant. We'd have to completely remake/simplify it, and that's very unlikely.
Why editor requires other location than game's folder and path to this location can't be longer than 50 signs?
Windows (since Vista at least) heavily frowns upon placing user files inside program directory. That directory is normally write protected, though Steam may actually change that (or just uses Windows' compatibility stuff). However, since people can install Trine games wherever they want, and we don't want overly long path names, different location is easiest.
The reason for 50 character limit is that editor limits max file + path name length to 200 chars. Windows has a limit of about 250 (you can code around it, but then e.g. explorer fails to access the overly long paths).
Trine 2 was the first game we released from our engine and we call Trine 2 engine/editor v1.0. Trine Enchanted Edition was the second game we released from our engine and we call Trine Enchanted Edition engine/editor v2.0. Trine 3: The Artifacts of Power was the third in line and, unsuprisingly, used an upgraded editor which was at v3.0. Shadwen and all our future games will be released from our engine/editor v4.0 (or even newer) which has lot's of new features. So if some features are missing (like UNDO) from Trine 2 editor compared to other editors, it's probably not a bug, just a missing feature in old engine/editor.
Can I play my MOD in online multiplayer game?
Yes. Just make sure all players are using the same game version and same MOD is enabled for all of you.
Can I play online multiplayer game inside the editor?
Not with other players over the internet. Editor is a development enviroment and it has only LAN (local area network) games enabled. LAN games are meant to test the online game functionality. You can host game from editor's GAME menu and launch a new client also from editor's GAME menu.