The election is made on the return and may not be revoked
What the document says“Any election made under this subsection, and any specification contained in any such election, may not be revoked except with the consent of the Secretary (and the Secretary shall provide such consent only in extraordinary circumstances).”
The section requires the election to name the nonresidential real property it covers and the designated portion, and to be made on the taxpayer's return for the year except as the Secretary provides, in the manner the Secretary prescribes. The election and anything specified in it may not be taken back except with the Secretary's consent, which is to be given only in extraordinary circumstances. The Secretary must issue guidance on what counts as substantial transformation and on how the recapture rule works after a tax free transfer.
What the document actually says“Any election made under this subsection, and any specification contained in any such election, may not be revoked except with the consent of the Secretary (and the Secretary shall provide such consent only in extraordinary circumstances).”
The choice may not be taken back. The Secretary may allow it in rare cases only.
The choice is made on the tax return. It must name the building and the part covered. Once made it sticks.
No action is recorded against this proposal. That is not evidence that none has been taken, and nobody has yet read it against the record. See what the tracker does not yet cover.