Add Two Or More Custom Resolution Modelines / Remove Default Modelines

[filevans]

Hello

I've tried to add 50hz and 55hz modelines, they work when one is added individually but I cant get both at the same time, I need 50hz for Amiga, C64 and Spectrum and I need 55hz for IREM M72 arcade games

These are the lines I added but only one custom modeline will show up at a time in lakka:

config.txt:
hdmi_group=2
hdmi_mode=87
hdmi_cvt=1440 900 50 5 0 0 0
hdmi_cvt=1440 900 55 5 0 0 0

cmdline.txt:
video=HDMI-A-1:1440x900@50 video=HDMI-A-1:1440x900@55

Most of the default modelines are useless and there are loads of them, is there a way to remove them all and just have around 4 modelines? (2 or 3 custom)