Is there any way I can load up single-frame images and create a time-lapse sequence with variable fps ?
Hi, and welcome to the forum and community.
Kdenlive creates videos with a fixed frame rate as per project profile/preset settings. When importing images as an image sequence you can specify the duration each image will be displayed. That can be just one frame, which, depending on the fps setting for your project, could mean that 30 images make up one second (30fps), or 60 images (60fps) are needed for one second.
In the project you can use the Speed Change and/or Time Remap feature to change the speed, but the final video you render will have the fixed fps you specified in the project settings.