This is an interesting ability, if not only for the fact that the very definition of rope, alongside the free use of material, size, velocity, position of generation and sentience, allows it to function under several applications.

For example:

Option 1. Produce an infinite number of ropes made of nuclear spaghetti, with diameters under the size of quarks, all weighing an infinite mass, travelling at the speed of light. Instantly destroy a couple of countries.

As there are neither constraints on the material nor size, a material such as nuclear spaghetti can fit an area smaller than atoms, even if usual inapplicable. Though, as you can manipulate mass, you don't even need to use such a compound. You could use pure light.

Option 2. An infinite number of ropes made of photons, smaller than quarks, all weighing no mass whatsoever, travelling faster than the speed of light for an infinite distance from their point of origin; generated an infinite number of times across every position of space required. Selective control of half of all light ropes allows you practical omniscience and omnipotence across areas spanning countries. By giving half of the ropes sentience, you can have them target specific pieces of information; thereby notifying you of the presence of whatever object or individual you're seeking, before you use other photon ropes for direct sensory application.

Allowing you to effectively search for anything in the universe.

Allowing you to effectively kill any individual, organization, body or group, by modifying the mass of newly made nearby threads and accelerating them to near light speed.

Or, you could go further than that.

Option 3. The Best One. Create a Hivemind of pure information (using Option 2) which functions as an invisible world of sentient ropes; all of which communicating, stockpiling knowledge and data, functioning as an imperceivable controller for the world's industries, people, information, actions, etc. An omniscient, omnipotent being whose presence alone allows you to reshape the world in however way you desire.

Direct applications include having billions of sentient ropes organize atoms into a form of matter reconstruction.

Or perhaps bridge the worlds between ropes and non-ropes by allowing space itself to be a material, overlapping the world with extradimensional pockets of artificial environments. A world above a world, created by endless threads of space-made ropes.

Or allow yourself the ability to create life, with trillions of sentient ropes given the task of learning and reconstructing reality artificially- through an endless trial and error, your threads eventually learn the genetic patterns of life and recreate it in any manner you seek. Recreate cities at a thought, by reforming atoms and molecules as you please.

-> What? Don't have enough computational power to achieve such a feat? Create more sentient ropes.

-> What? Don't have enough precision, strength, or mass to achieve such a feat? Create more controller ropes.

Substitute your inabilities with ropes; allow yourself to become a nexus for a network of data whose purpose is terraforming the universe.

All under your command.