Allow configuration of the sidebar and icons.

[develroo]

Checklist

• [X] I have used the search function to see if someone else has already submitted the same feature request.
• [X] I will describe the problem with as much detail as possible.
• [X] This issue only contains a request for one single feature, not multiple (related) features.

App version

8.0b5

Problem you are trying to solve

Currently Thunderbird app autogenerates label icons and differentiates them by colour and domain name. This become confusing when you have multiple accounts with the same domain name. Here is an example.

Suggested solution

Either give the ability to manually choose the labels or hide them completely and just have a drop-down to select an account like there was in K9-Mail

Screenshots / Drawings / Technical details

Same image as above. I think it demonstrates the problem clearly.

[kewisch]

Duplicate of #8381

We're looking into more customization options, this is a much requested feature :)