Re-establishing Digital Certification for VBA Project

[Art]

I would like to establish a self-generated Digital Certification for a VBA
Project so that when I open an Excel file with a macro (the VBA project) I
won't receive a macro warning every time I open the file.

I previously established such a certification but recently changed the macro
and lost the certification and associated trust for the digital signature.
Now, I can't re-establish the certification, delete the digital signature
that is no longer trusted or recertify the signature. Is there anyone who
knows how I can re-establish a self-generated digital certification for a VBA
project after the initial certification is lost.

Is there any good reference material on Digital Certification for a VBA
project? The Office Help material only seems to offer some limited
information on the initial setup or establishment of Digital Certification
for a VBA Project. It doesn't address how to re-establish certification
after it is lost or how to delete digital signatures that are no longer
trusted.