There are two options; you can install the old editor via a plugin (look for the Tiny MCE plugin on your Admin home page when you log into your WordPress site):
Or, use a "Classic" block in the Gutenberg editor. Here's how to find the Classic block the first time you use it:
After it has been used one time it will appear on the short cut list when you click that plus sign at #1.
The Classic block is inserted into the page where your cursor was; it does not change the entire page and add the toolbar buttons at the top. In the page, where your cursor was when you added the
Classic block, you will see this:
If the second and third rows don't appear, click the "more icons" button at the top right ... it has a fine line around it in the image above. Then you can use the Merge Fields and Short Codes drop down, and click the Custom Login Page icon for all the functions you are used to.
The rest of the PilotPress settings are still in the sidebar, but Gutenberg may push them down the page. Scroll down in the sidebar to see them.