From the account of each user, go to MENU > Set up my devices > HS5 (Select your scale) > Delete user .
Then select the user to be deleted, here: user n°7
Note - The scale must be connected to the internet. Deleting the user will not delete his data synchronized with his account.
*credit to Sylvain of iHealth Labs EU
https://helpcenter.ihealthlabs.eu/hc/en-gb/articles/115005876345-iHealth-HS5-How-to-delete-a-user-of-the-scale-
https://helpcenter.ihealthlabs.eu/hc/en-gb/articles/115005876345-iHealth-HS5-How-to-delete-a-user-of-the-scale-