My default paragraph style is ‘Default Style’. I defined a new style ‘default2’ with line spacing set to proportional, 130%.
I recorded a macro ‘bigspace’ to change the current paragraph’s style to ‘default2’ and another macro ‘normalspace’ to change the current paragraph’s style to ‘Default Style’. How to record a macro, Recording a Macro - LibreOffice Help
I defined a global variable ‘linespace’ and a third macro ‘switch’, i.e.
if linespace=0 then
I assigned the macro ‘switch’ to the key ‘Alt+.’ since I did not find that ‘Alt+/’ was an available option. To assign a macro: Tools>Customize>Keyboard. Select the shortcut key ‘Alt+.’, then in the Functions area select LibreOffice Macros and navigate to the macro in your file called ‘switch’, then click the Modify button to complete the assignment.
To use this toggle: Place the cursor in a paragraph and key ‘Alt+.’. The ‘linespace’ variable doesn’t know about the spacing of the current paragraph so you may need to press ‘Alt+.’ twice to toggle the spacing. This will replace any paragraph style you have set manually with either the default style or the wide-spaced style so be sure that’s what you want.