I see no reason to cite the finding aid (the index entry) instead of the thing it helped you find (the image):
FamilySearch Film # 007595352 Image 19 of 186 (Columbia, Maine, Town and vital records, 1796-1860): Mr. Sewel Labbaree & Miss Sally Sawyer, March 21, 1805. (
https://www.familysearch.org/ark:/61903/3:1:3QS7-99N7-X4YK?i=18)
If the image had locators like page numbers and entry numbers, I'd include those in the citation, but there are none in this case.
If you want, you can add the microfilming information from the FS catalog entry (Salt Lake City, Utah : Filmed by the Genealogical Society of Utah, 1955), but I generally omit it: it would not help anybody find the image if the link broke.
What I do generally include is a full transcription of the relevant entry:
Mr. Sewel Labbaree & Miss Sally Sawyer boath(??) of Plantation No. 22 was publishd March 21st 1805 in Columbia by Wm Buckmann T. Clerk
No, there isn't a button you can conveniently push to generate such a citation, but they're not that hard to write, especially once you realize that the order and format doesn't matter one whit, as long as all of the necessary details are there somewhere. (I know it's hard to override those decades of conditioning about manuals of style and rules and stuff, but you can do it!)