Well, after much reading of the instructions, I finally created a source template in RootsMagic. I highly recommend reading all of the instructions in the help menu on source templates and source template language before endeavoring into this. Basically, I copied the template for the state-level certificates online images and added a few additional fields to make it work for a state register online image. Adding the fields was easy enough. The hard part was getting the language right in the footnotes.
For example, some of the Michigan birth registers at FamilySearch Labs reference the volume number and page number, but some only reference an item number and a page number. I know from using FHL microfilm that item number is not always synonymous with volume number. In the cases where an item number is referenced, then instead of putting Michigan Secretary of State, Birth Registrations, 1870, St. Clair County, 8: 118 in the footnote, I need it to say Michigan Secretary of State, Birth Registrations, 1870, St. Clair County, p. 118.
Overall, I was excited that it is possible to get a footnote to say this. It's done with what RootsMagic calls switches. Switches are somewhat like if/then statements. For example, "if the Volume field has content, use this format, and if not, use the other format." I just had to study them for about 30 minutes to understand them in their full capacity. RootsMagic has some good examples in the help menu instructions to help users understand how to use switches.
Another thing I like about RootsMagic is that I can still share an event with witnesses that are not in my database. Once I enter a marriage, I can click on "share" and then choose to type in the name if it is not someone already in my database. Once I am done, I can click on the "share" button again, and the names of the two witnesses to the marriage pop up. This is just nice because the witnesses, whether or not relatives already in the database, can be easily found. In Legacy, I have to open up the master source detail screen and look at the text for the marriage record, if I chose to put the text of the source in the database. Or I have to open up the image of the marriage record, assuming I attached that to the source detail. Also, in Legacy, if the witness is not in my database, I have no way to attach a source to him/her.
I'm just still trying to decide if I really want to do another software conversion. I think I do, but it's hard to commit to reformatting all my sources. I still need to play around with the reporting features. I need to go back to my genealogy to-do list and see what kinds of reports I am using for each family file. I need to make sure RootsMagic can produce these reports. I'm sure that it can, but I still need to verify before fully committing to the switch.