I would consider cutting it back hard and doing a major trunk chop. Identify a new leader low down, maybe a few nodes from the root flare, and start developing taper and movement.
It’s really easy to propagate Portulacaria afra via cuttings, so you can probably chop this up into multiple plants.
The foliage is quite sparse and leggy, so it probably wants considerably more light. Consider putting it under a grow light and/or moving it outside when it’s warm enough.