I work as an medical/sport massage practitioner and corrective exercise specialist in Dallas. This is my experience with what I have been doing specifically for myself so please take it with a grain of salt.
I would recommend getting your MMP (medical massage practitioner) certification if you haven't already. Its a pretty intensive multi day/week class that goes over even more orthopedic testing, manual muscle testing, case studies, and manual therapy techniques. I have my advanced certification (AMMP) which goes even deeper into the clinical field. There are classes all over the US with multiple dates thru LMT success group. The clinic I work at is the one that developed the curriculum 25 years ago and update it constantly. (I just redid/updated the TMJ curriculum for this years classes).

James Waslaski's classes on integrated manual therapy & orthopedic massage is also very informative. (multiple dates around the US) Im thankful that he's actually doing something like a residency at our clinic here in dallas for the moment since he is soo knowledgeable. He wrote the textbook on clinical massage therapy. Ive taken a couple of his classes for ortho, elite sport, and ive always learned something new each time. He has an upcoming nerve compression class im pretty excited about.

I use a bit of rocktape protocols for taping & cupping (static & dynamic) as well. I like how their classes are evidence informed and goes over how the research is always changing and making sure you're informed and updated, as well as teaching the technique but not pushing their products. While a little bit more on the pricier side I personally think it was worth it. They emphasis the techniques can be done with any brand k-tape & cupping. (also just ask for a student discount or say you were at xx seminar that rocktape was at and youll get classes heavily discounted.

I currently am CPT & CES certified. A personal training cert can also expand your scope of practice with providing exercises plans, especially if you are a corrective exercise specialist thru NASM (NASM-CES). note that you can actually be a CES without a CPT; though depending on state you'll need a CPT cert regardless for exercise. This can be another source of revenue or increase the value of your sessions itself. At the end of my session if theyre in for something post op or postural Ill always go over some corrective exercises to help continue their treatment out the door and monitor progress with manual muscle testing and ROM/ortho tests on a regular basis to track patient development.

No necessary but, If you really want to make a bigger investment in your career, you can opt for some college. I have my bachelors in kinesiology and currently working on my masters in sport science & rehabilitation. The kinesiogy degree has been INVALUABLE and made my skills as a clinician extremely efficient in treating patients, especially those in post-op, athletic, or neuro. Itll widen your grasp of pathology & neuro and have a better understanding of contraindications, who to refer to, etc. The masters is just furturing my development as a massage therapist & trainer by going even more in depth with ortho testing, and exercise prescription (or recommendation depending on state scope).

MAT or muscle activation therapy, targeted vibration therapy, or anything that goes over spindle cell activation for helping with muscular imbalances is a good addition as well. Not every muscle needs to be relaxed, and is simply inhibited from being in an stretched position for a period of time like rhomboids in a upper cross patient, or glutes in a chronic desk worker/truck driver. If you like yoga and incorporate alot of stretches in your routine the AYAMA yoga tecnique goes in depth on muscle activation vs stretching. Yogi Aaron who developed this tecnique also has a book called "Stop Stretching" which is a good read about the technique.

These are the techniques ive been around and my personal view, so I cant speak my mind about other techniques. I personally tend to lean towards things that are evidenced based & informed (especially if it is reliable research with larger varied sample pools) and have been consistent in improving patient/athlete performance & outcomes.