In the attached object editor of ModelConverterX you can add lights to your object. On export to FSX these lights will be converted into effect (FX) files. Besides the colour you can now also specify a blink duration for those lights. This means you can create flashing lights.

If you enter a blink duration of 0 seconds you get a static light as before. If you enter 1 second you will get a light that is on for 0.5 seconds and then off for 0.5 seconds. If you enter 3 seconds for the blink duration you will get a light that is on 1.5 seconds and then off 1.5 seconds. I guess you’ll get the pattern. The smaller the number, that faster is blinks.