typography - How to generate one font file consisting of multiple font weights (i.e. multiple font files)?

I have multiple font files, each of a different weight. The problem arises when they are used in, applications and Wordpress. For example, they appear like this:

  [family]         [weight]
 - sailec-light   - regular
 - sailec-regular - regular
 - sailec-medium  - regular
 - sailec-bold    - regular

Because of this, every time I switch between these weights I always have to click the dropdown that's the Font Family, and never the Font Weight, because all four exists in the Font Family section, leaving the Font Weight section completely unused and always pointing to "regular". This makes my font family list messy, and

I would like to have them be one single file (i.e. one font family). Like this:

  [family]  [weight]
 - sailec   - light

            - regular
            - medium
            - bold

I already tried RoboFont to combine them by changing the family names and style names but haven't been successful because RoboFont opens each .otf file in a separate window, and I don't know how to generate one single font file that is the combination of all four.

The problem with this is that in Wordpress I can only upload one font family to be the body font. So if the font file that I upload is regular doesn't include bold, then I will never be able to use bold in my body text.

Any help appreciated. Thanks.