Mine went from 2.5 mins to open, to 1-2 seconds.

see https://blog.sqlauthority.com/2018/05/07/sql-server-restore-database-wizard-in-ssms-is-very-slow-to-open/

MSDB.dbo.backupset keeps a log of backups (separate to what's inside backupfiles themselves).

Try

select *
from msdb.dbo.backupset
where database_name = 'Your-DB-Name-Here'

To clean up:

EXEC sp_delete_backuphistory @oldest_date = '2019-06-27 10:00:00.000';

The date above is an example.

It is recommended to include this kind of thing in your maintenance plan.

Mine went from 2.5 mins to open, to 1-2 seconds.

see https://blog.sqlauthority.com/2018/05/07/sql-server-restore-database-wizard-in-ssms-is-very-slow-to-open/

MSDB.dbo.backupset keeps a log of backups (separate to what's inside backupfiles themselves).

Try

select *
from msdb.dbo.backupset
where database_name = 'Your-DB-Name-Here'

To clean up:

EXEC msdb.sp_delete_backuphistory @oldest_date = '2019-06-27 10:00:00.000';

WARNING: the sp_delete_backuphistory procedure isn't limited to one database, there are no other parameters for this procedure call

The date above is an example.

It is recommended to include this kind of thing in your maintenance plan.