I am using one SharePoint Issues Tracking list.
How do I to write comments in a SharePoint issue tracking list without editing the other fields?
Please help me.
There's no OOB mechanism to do this. When you save a list item, you're saving the values of all columns, and there is no mechanism to save just one column. This also means that we can't give permission to a user to be able to modify just one column.
A developer could certainly create an application that allowed the user to populate the value of one field (though the SharePoint restrictions above would still apply.) It might be possible to create a power app that switched certain fields into read only mode based on some condition, though last I checked, Power Apps had difficulty with the versioned multi-line text fields like the issue tracking comments field.