UX improvements to expression editor

[fti]

I think several things should be done to improve user experience:

1. Display the @ prefix used on variables / table records / … : Not having it displayed is especially annoying when copy-pasting an expression since these must be reinserted by hand. This is also an unintuitive and non-standard practice ; any syntax highlighter I know does one thing 99% of the time: they format the text. They almost never edit/alter it (if we exclude whitespaces / indenting).
2. Add a copy-paste button somewhere: I regularly need to copy-paste an expression. This currently requires to display the expression editor (or its preview) and to manually select the text. It would be much handier to have a simple copy-paste button displayed next to Enabled state / trigger expressions that would not require any manual selection or opening the expression editor/preview.
3. Allow to search @ values without forcing the user to type everything: Currently, if I want to look for @``Users.John Doe.Email, I cannot simply type john for example. I have to type @users``.``john. This is especially annoying with long prefixes like @Machine Activity Field, @Last Machine Output, @Table record.

[thorsten.langner]

@fti

1. Display the @ prefix used on variables / table records / … : Not having it displayed is especially annoying when copy-pasting an expression since these must be reinserted by hand. This is also an unintuitive and non-standard practice ; any syntax highlighter I know does one thing 99% of the time: they format the text. They almost never edit/alter it (if we exclude whitespaces / indenting).

As a short addition: In the Trigger Panel, copying the expression also kopies the @ character. In the enabled state e.g. it does not…