Uninstalling without losing diagram text

The app keeps no data of its own: every diagram's text is part of your pages. What happens to it after an uninstall depends on where it sits.

The text is in	After the app is uninstalled
A code block on the page, drawn by an empty macro	The code block stays on the page as normal Confluence content: readable, searchable, exportable. The empty macro shows an error box.
The macro itself (the usual case)	Confluence hides the macro's contents and shows only "Error loading the extension". The text is not deleted: installing the app again shows every diagram again.

The second case is how Confluence treats any macro whose app is gone; no app can change it.

Before you uninstall: move the text onto the page

Do this for each diagram you want to keep readable without the app. The editing window guides it, and it never empties a macro until the text is on the page.

Edit the page. Click the macro and press Edit (the pencil).
Choose Move text to the page, under the diagram text. The window copies the text. If your browser does not let it, the window shows the text selected: press Ctrl+C (⌘C on a Mac) to copy it.
Press Cancel. On the page, right above the macro, type /code, press Enter and paste the text into the new code block.
Click the macro, press Edit again and choose Move text to the page again.
Once the window says it found the text on the page, choose Empty the macro. The macro now draws the code block above it, so the page looks the same. If it does not say so yet, publish the page and open the window again.
Publish.

After emptying, the window offers Put the text back in the macro while it is still open. Later, Edit on the empty macro offers Write the diagram in this macro instead, which copies the code block back.

The window offers the move only for a macro that holds nothing but its diagram text, so emptying it loses nothing else. A macro that also holds other content, such as a note beside the code block, is moved by hand:

Edit the page. Click the macro and press Edit (the pencil).
Select all the diagram text in the window and copy it. Press Cancel.
Right above the macro, type /code to insert a code block, and paste the text into it.
Inside the macro's box, delete its code block, so the macro is empty.
Publish. The empty macro now draws the code block above it, so the page looks the same.

After the uninstall the code block stays readable.

Exports keep the text too

A Word export of the page shows each diagram's text as a code block, so an export made before uninstalling keeps it. See PDF and Word export.

If your subscription ends

Each diagram still draws, with a one-line notice under it and in the editing window, which still saves. Nothing is hidden or deleted.