The complexity of your work will gradually increase as you build up confidence and skills. When that time comes, you will need to temporarily mark your fabrics and no longer just marking seams and cut lines where no-one will see the permanent marker’s strokes.
I find that even on high-tech fabrics, the most versatile and reliable method to mark temporary guides and lines is chalk. I use a combination of a Tailor’s chalk pen and 4.5x3cm Tailor chalk rectangles in an assortment of colours to be able to always have contrasting markings on any colour fabric. On full set will probably last you forever if you are a casual builder like me.
You will want to precisely mark your webbing and draw lines and patterns on a lot of your materials to help with alignment, folds, assembly orders, and many other writings but also want to be able to easily wash it off when the build is complete.