When you can't find your secret anymore, but can still access your funds, rekeying your account may help you
Imagine this situation: you have lost the secret key, but can access the account on XUMM.
You can still access your account, but can't import your account on another/new device as you'll have to enter your account secret there.
Security is the reason for XUMM not allowing you to view/export your secret once imported. More on that: here
The only way to get full access to a fresh secret for your existing account is to either:
Send all of your funds to another account
Create a new account in XUMM
Make sure you properly back up your secret key
After that send the funds to the newly created account
Delete the old account using a secure 3rd party tool: https://xrpl.services.
A guide on how to do that here
Using this tool you can retrieve the last 8 XRP out of 10 XRP (account reserve).
Please note: as this method generates a new account, your account address (r...) will change as well!
Suggested solution (you keep your r... address):
Configure a new secret to your existing account, also known as "rekeying an account".
More on how to do that here
Now you don't only have access to your account in XUMM, but you can also sleep well (again) as you know you have your secret backed up safely, offline, ready for import/recovery if your phone is lost/replaced.