In Thunderbird for Android v8.2 I have seen this display of the opened burger menu.
The readability suffers as too much information is squeezed in a row:
The result is that folder names are more often broken into several lines. 😥
In K9Mail (v6.9) the icons of the left column (account selection, settings) were vertically above and below the folder list. This reduces the necessary total width. Please consider to revert this change. The screenshot above was taken on a big screen with a system font size, bigger than normal (visual impairment 👵👓).
Additional improvement may be achieved by hiding the [Google Mail] or [Gmail] prefix (see Folder naming for Thunderbird mobile).