If you want to disable current(cursor line) line highlight in Geany IDE it is very simple you can disable highlight current line in any or default colour schemes. Follow given steps these steps are for linux users.

Step-1) Open Home partition in file manager.

Step-2) Go to your username and enable show hidden files;you can enable it by pressing (ctrl+h) or by right clickin and finding that option.

Step-3) Find (.config) folder by manually or by using search option.

Step-4) Now go to (geany) folder.

Step-5) Go to (colorschemes) folder.

Step-6) Now open themefile which you want to disable highlight cursor line in any text editor.

Step-7) Scroll down and find (current_line=1a1a1a;true) replace 'true' to 'false' like below (current_line=1a1a1a;false). Then save and exit.

Note--- Here it is not necessary that colour name is '1a1a1a' it should change according to your scheme looks like some are '#6f6f6f' and another. Your main task is to replace true to false and than save and exit.

These are paths for easily understand:-

File manager > Home partition or folder > enable hidden files or finding '.config' > geany > colorschemes