“Could not save (file name) because the file is already in use or left open.”

If you’re on a mac getting this error, try this for a solution:
Force Quit on Finder so that it restarts.

There may be several solutions, so this may not necessarily be the fix for you, but give it a shot!

All these years and I had no idea that I could do this, well here’s how it’s done.

1. Draw shapes drawn in different layers.

2. Select one of your shape layers by clicking on the square to the right of that layer. You’ll know if you did this correctly because it is outlined with brackets.

3. Hit Copy (Cmd + C).

4. Select another shape layer in the same way, you need to get the bracket around the right box so you know you’re selected.

5. Hit Paste (Cmd + V).

Wheee! Now go crazy merging your shapes nerd!