Can we use 2 Flying shear blocks in single LMC058 controller.
Yes you can use two flying shear on the same controller. LMC058 controller can handle 8 synchronous axis simultaneously.
But you need to take care that if you want to sync two slave from one master then you must configure two logical axis for master axis and then Link individual Logical axis for each Flying Sheer FB. The reson behind this is using AFB's such as Flying Shear or Rotary Knife write some value as Master Offset value to Softmotion axis linked to master axis to get the next Sync point for the connected Slaves baiss on the TouchProbe point and Cut to length point. If you are using common SoftMotion axis for both the slave as master then both the function block will write different Master offset value and create malfunctioning for both the Slave axis to get the next sync points.
Apart from above there is not any limitation in using the number of Application function blocks.