When will be the Edit Theme for mobile will be fixed? I noticed that it's almost been 4 years since BlacckSh33p brought this up.

The theme editor is currently not suitable for mobile use due to the size constraints. The button to open it is hidden on smaller viewports. If you enable desktop mode on your device and make your viewport wide enough you may be able to access the button to open it. We have no plans to create “mobile” versions of the theme editors at this time