Power Query Editor slow - renaming alone takes 5 minutes

It can be slow unfortunately. It depends on how fast your connection is, how your transformations are happening, etc. If you have a few hundred thousand rows in Excel or a CSV file, doing an initial filter, renaming, etc. goes fast. But if you do merges, groupings, etc. then that requires Power Query to load more and more data to do the work.

Make sure that you have told Power Query to only give you column profiling on the first 1,000 rows. That is the default, but if you changed it it will slow things down considerably. It is in the lower left corner of the app.

One thing you can do that sometimes helps is buffer previous statements. So after a grouping, wrap the entire thing in Table.Buffer() in the formula bar, or List.Buffer() if it is a list. You can remove them all later if desired once you are done coding.

You can also rename steps faster in the Advanced Editor, but you need to know what you are doing. Unlike doing it in the US, the advanced editor will not automatically change subsequent steps that relied on the first name. You have to manually fix those too, or the code simply breaks until you do fix it.