UI Themes / dark theme
Add a way to support UI theme (change colors of UI), implement dark theme
Better annotation support
The basics of annotation tools are already present, and they work really well! But compared to other pdf viewers, the tools are quite limited and not really user friendly.
Active tab color
For those of us who do not see well, it would be very useful if the active tab was a little more differentiated from the rest.
Bring Back EPUB Fonts/Layout Customization
Customization of fonts type and size, as well as page layout for EPUB disappeared in v3.4. Please bring it back.
Allow customizing toolbar via advanced settings (add more actions and remove / change order of existing actions)