Clean Text hasn't a specific feature to replace a specific number space characters with a tab, anyway you can easily create a macro to perform this task, here is how to do it.
- Enter in the main window of Clean Text a tab using the Tab key of the keyboard, select it and then copy it.
- Go in the Macros pane.
- In the "Macros for text replacing" section, click Edit.
- Click on the Add button.
- Give the new macro a name, for example "Replace 3 Spaces With 1 Tab".
- Enter 3 spaces in the "Replace:" field.
- Paste the tab you copied in step 1, into the "with:" field.
- Click "OK".
- Click "Done".
- Now you have your new macro ready to use. Just click on it in the pane when need it.