Sword Searcher works great with Parallels, however, every time Mac upgrades the OS you have to pay $50 for the Parallels upgrade, which leaves you with the choice of either not upgrading your OS (which is a free upgrade from Apple) or paying the $50 for the Parallels upgrade. I was using Parallels version 9 when my logic board died and the company that repaired it also upgraded my OS, now I have to buy Parallels version 13 if I want to continue using Sword Searcher I have been a beta tester since Sword Search v 5 or maybe 6, after all these years I sure would love to beta test a Mac version
Your other option is to use a free VM like VirtualBox instead of Parallels. The only reason I suggest Parallels is because I have been told by Mac users that it is reliable and easy enough to use and integrates well and offers customer support. @Eric uses VirtualBox.
Yes, cybresaint, I use VirtualBox to run SwordSearcher all the time, and it's free. (Well, there is a catch: you have to buy Windows.*) But you have to spend some time learning, and once in a while something goes a bit off the rails for a while. However, I have always been able to get good advice from the VirtualBox website (https://forums.virtualbox.org). You might want to give VB a try if you're willing to buy Windows. At $50/year for Parallels (assuming OS X gets updated once a year) vs. the cost of Windows 10, though, I'm not sure what I'd choose. If you're tech savvy and like to learn and think Windows will last enough to make the initial cost of it less than Parallels, it might be worth it.
(*If you do get Windows 10, I do not recommend the Home version, which is what I have. I'd go with something higher than that, I think it's called "Professional". The Home version doesn't let you control updates very well, and once in a while I come to my computer in the morning and Windows 10 has updated itself overnight and messed things up.)
Eric here's a YouTube video from a tech guy I follow (Britec09) on stopping windows updates. I wouldn't stop them completely, but this allow you to control it with an on off switch. Seems to work well so far.
I run Windows on my MacBook Pro (2009) using Bootcamp (i.e. when I switch on I choose to run either with Mac OS or Windows). Windows in this mode is lightning fast and SwordSearcher runs perfectly. Parallels or Fusion are fine but unless you have a mac with plenty of RAM and able to run the latest OS then running Windows (and therefore SwordSearcher) is painfully slow. I would recommend using BootCamp (free with all Macs) as the only way to run SwordSearcher.
FWIW - I run SwordSearcher on a newer Mac with Parallels, but also have a VirtualBox VM and it runs fine in both.
I started off with VirtualBox, but I do commercial SW development so couldn't use it free for that--plus I've found Parallels to be a superior VM solution for macOS over both VMware and VirtualBox. But that's mainly when pushing things into technical corners such as USB device support and seamless integration between the Windows/Mac file systems.