If you delete a holding, Parqet also deletes all its activities. This works on the web and in the mobile app. In the mobile app, long-press the holding in the holdings list and confirm “Delete holding?”.
Here's how it works on the web:
Open the holding, click the three dots “⋯” at the top right and then “Manage”.
In the dialog, click “Delete” at the bottom left and confirm.
You can't restore deleted data.
You can't delete holdings from Autosync. They would come back with the next sync. If a reference account is linked, Parqet removes the related offsetting entries and recalculates the account.