Dictionary entries for wager as a noun or verb include:
(noun) That on which bets are laid; the subject of a bet
(verb) To bet something; to put it up as collateral
Usage of “wagered on” and “wagered upon” can be seen in links obtained via ngrams for wagered on,wagered upon. Wagered on is used substantially more often than is wagered upon. Examples include
• The gross commission shall be first deducted from the gross amount wagered on each individual pool...
• If the book is balanced in terms of amounts wagered on each side of the proposition, what is the outcome for the sports book?
• The money wagered on these three horses totals $2,000 and is distributed as follows: ...
• “I never wagered upon your honor, Llewelyn. I wagered upon your common sense."
• The new Madison Avenue guard, in contrast, wagered upon the attractiveness of the messages of U.S. popular culture ...
Returning to your question, if you place a bet on a payline, it is reasonable to say you have wagered upon it. Calling that payline a wagered payline is possible, but perhaps a stretch. Calling it a covered payline might be better.