Compare parent revision with working tree

I need to revert changes from a previous commit, but only selectively, not the complete file. There may also be other uncommitted edits already done to the working file. From the compare view (I use Beyond Compare) I can select each change and whether it needs to be reverted or kept. This cannot be done directly with TortoiseGit currently.

What I'd need is a new command from a file in a commit: "Compare parent revision with working tree", below the existing command "Compare with working tree".

• The left side is the parent commit because that contains the original state that I need to revert to. (Same as "Compare with base")
• The right side is the working tree because that is writable. (Same as "Compare with working tree")
• The command is on the commit that introduced the change (and not the parent) because that commit lists the file and can also show the changes that were done in that commit.

Workaround: Use the "Compare with base" command to open the compare tool with the before and after file, then drag the corresponding file from the working directory onto the right side to compare with that instead of the commit's version. (Beyond Compare allows that, not sure about other tools.)

Maybe there's a better way to solve this but I don't know it.