Improve submodel indentation

[Alkly47]

Is your feature request related to a problem? Please describe:

Did the indentation in the sequencer change at some point? Or is it just now bothering me? Regardless, it is only a single character...
This makes it difficult to locate the top-most "parent" model/group when ready to collapse the expanded list.

Describe the solution you'd like:

Add additional indentation, or add an option to increase it, so that it is easier to differentiate where the "parent" model/group starts vs layers, grouped models, or submodels in the sequencer.

Describe alternatives you've considered:

An icon, or hyphen, etc., preceding the submodel/layer or "parent" model/group, or even different colors would be helpful. Anything to help differentiate them from the top layer/group/model would be great. Options to tailor it to the user's preference would be even better!

Additional context:

At first glance, differentiating the model vs submodel is difficult.... I'm hoping it can become more obvious.

[cybercop23]

Yeah.. @derwin12 tried a variant. The grid can use an UX overhall.

[derwin12]

#4408
Yea .. I removed my attempt because it too was flawed.

[cybercop23]

Yea .. I removed my attempt because it too was flawed.

You are you own critic. We all liked it. I guess something to add to the list for next month... Hehehe