Keyframes fast selection

One more time, I swear I am human. 

Try selecting the a few keyframes then use shift+r to repeat the pattern of selection. I don't know if blender will detect that pattern but that's all I've got.

Lol... I'll take your word for it Dwayne.

That was a great idea, but unfortunately it didn't pan out. I did it manually, it was only 8 seconds of animation. But if anyone knows the way, let me know... cause I definitely don't want to do it again if I can avoid it.

Sorry about that, but Everytime I tried to post it kept telling me I wasn't human. 

Found a solution: https://blender.stackexchange.com/questions/264754/how-to-deselect-one-keyframe-every-nth-on-a-multiple-objects-selection

You have to enable Developer extra and then use F3 to search for Deselect. It has every 2, every 3, and every 4. I've tested on 4.2 and 4.4 and seems to work fine. If I find the time I'll see if I can link the operations to a menu. 

***Edit*** Forgot to mention I added to the select menu on the dopesheet editor.

Well, that was surprisingly easy. I just added an append to the register and a remove in the unregister.

bpy.types.DOPESHEET_MT_select.append(menu_func)
bpy.types.DOPESHEET_MT_select.remove(menu_func)

So the whole script is:

bl_info = {
    "name": "Partial Deselect",
    "blender": (3, 0, 0),
    "category": "Object",
}

import bpy

def main(context, nthkey=2):
        for action in bpy.data.actions:
            for channel in action.fcurves:
                for key in channel.keyframe_points.values()[0::nthkey]:
                    key.select_control_point = False
                    key.select_left_handle = False
                    key.select_right_handle = False

class ChannelSelect4Key(bpy.types.Operator):
    """Partial deSelect"""      # Use this as a tooltip for menu items and buttons.
    bl_idname = "anim.channel_select_4th"
    bl_label = "DeSelect 1 keyframe every 4 keys"
    bl_options = {'REGISTER', 'UNDO'}  # Enable undo for the operator.
    def execute(self, context):
        main(context, 4)
        return {'FINISHED'}

class ChannelSelect3Key(bpy.types.Operator):
    """Partial deSelect"""      # Use this as a tooltip for menu items and buttons.
    bl_idname = "anim.channel_select_3th"
    bl_label = "DeSelect 1 keyframe every 3 keys"
    bl_options = {'REGISTER', 'UNDO'}  # Enable undo for the operator.
    def execute(self, context):
        main(context, 3)
        return {'FINISHED'}

class ChannelSelect2Key(bpy.types.Operator):
    '''Select odd keys for selected channels in the dopesheet'''
    bl_idname = "anim.channel_select_2nd"
    bl_label = "DeSelect 1 keyframe every 2 keys (even)"
    bl_options = {'REGISTER', 'UNDO'}  # Enable undo for the operator.
    def execute(self, context):
        main(context, 2)
        return {'FINISHED'}

def menu_func(self, context):
    self.layout.operator(ChannelSelect4Key.bl_idname)
    self.layout.operator(ChannelSelect3Key.bl_idname)
    self.layout.operator(ChannelSelect2Key.bl_idname)

def register():
    bpy.utils.register_class(ChannelSelect4Key)
    bpy.utils.register_class(ChannelSelect3Key)
    bpy.utils.register_class(ChannelSelect2Key)
    bpy.types.DOPESHEET_MT_select.append(menu_func)

def unregister():
    bpy.utils.unregister_class(ChannelSelect4Key)
    bpy.utils.unregister_class(ChannelSelect3Key)
    bpy.utils.unregister_class(ChannelSelect2Key)
    bpy.types.DOPESHEET_MT_select.remove(menu_func)

if __name__ == "__main__":
    register()

Or you can download and install as an addon.

https://drive.google.com/drive/folders/0B5x4OjbuDbY5fmxRWXprNTItWEVFMmhhTFRCSkFlZ2RuS2YwcW4wMHhQQW04ekdPV25aVms?resourcekey=0-PQxdYmfIoaVYZ96YbJtmnw&usp=sharing

Wow! Incredible! Thank you Dwayne, I'll test it out right away!!