[White Tie]

Originally Posted by lucas_LCS

can you use it to say, create a sidebar if the FX button is active?

You can't do anything to make a sidebar; MCP panels have a width that is defined at the layout level and is then fixed. This is a limitation within Reaper itself.

Originally Posted by jrengmusic

I don’t know if there is any syntax in WALTER to have track selection as variable.

You don't know correctly It can't be done.

Originally Posted by Lunar Ladder

Usually in audio contexts red is right, and white/black/blue is left. Like in standard RCA leads. Or any color coded L/R channel thingy.

This is a topic we have discussed at length; I wish there was one convention I could blindly follow, but there are two conflicting approaches and it would be naive to suggest an obvious 'right' answer. Audio does indeed have a cabling convention, but I know of few examples where it has been carried onto hardware human interface, where they are usually both labelled the same colour and solely the text/location used to facilitate at-a-glance recognition. Software UI, on the other hand, does have a convention, and it is to follow the naval/aerospace convention of left-red, green-right.

So; whether you use no colour (hardware), red-black (cables) or green-red (software) comes down to whether you expect REAPER to behave as a piece of software or as a representation of a piece of hardware.

On to this I layer my own user testing which (anecdotally) suggests that people broadly find a colour difference useful, and red-green most visible and expected. And in such a no-right-answer situation, that makes it the least objectionable compromise. I would welcome further discussion on this, though ideally not as a derail of this theme thread