1
You can scale the entire user interface by setting a custom screen resolution.
Open the Preferences dialog from the Tools menu, then under General → Appearance → Screen resolution check "Set a custom high DPI scaling" and possibly adjust the default value of 1.5 as you see fit. You will then be prompted to restart Spyder for the new settings to take effect.
This will increase the display size of all fonts, including the one used in the editor, which can however be customized separately.
Partly this solved the problem, since the editor font size is controllable by itself as you pointed out. But apart from the editor's font size, the relative proportions are completely wrong: E.g. the filenames are now readable, but the symbols are now huge. So ist still not the desired output! – ueli – 2019-08-21T12:19:10.933