Why is there no delete message on toolbar?

Tap the More (...) button at top-right of the screen to expose the Customise Toolbar button:

Select Customise Toolbar...

Select the additional icon buttons that you wish to see - and when finished tap Done.

Check your Mail account settings:

Settings > Mail > Accounts > [Your Gmail Account] > Account Settings > Advanced > [Move Discarded Messages Into]

Select Deleted Mailbox

To which "toolbar" do you refer? Are you having difficulty with a particular App?

What, specifically, are you attempting to achieve?

To further clarify, are you using the iPad's native Mail App with your Gmail account - or are you instead using the Gmail App?

I'm struggling to understand precisely what you are having difficulty with.

Perhaps you refer to visibility of one of these two trash icons...?