SPF record modification

[Jukebox6523]

I'm on a workspace trial with an existing google domain. Workspace has created an SPF showing:

v=spf1 include:_spf.google.com ~all

I wish to modify it to:

v=spf1 include:_spf.google.com -all

However, when I enter the admin console to manage it, there is no "View Details" in the status column. Going to the DNS setting in google domain, the workspace setting has a "manage" option, but it simply takes me to my email settings. 

I could add a custom spf record, but I cannot delete the workspace spf record without deleting the adjoining settings. 

Can anyone offer advice on how to modify the spf record as described?

Thanks, Jerry