Hi, if you soft delete a transaction then it wont re-appear on next sync. In some cases even if you permanently delete a txn, it may not appear on next sync right away but you can bring it back in by going to the Wallet > Troubleshoot > Sync from beginning which will import any permanently deleted txns.
You should soft delete the txn then add your own manual one with any changes you want, this will prevent the importer from bringing it back in.