Reuse changable logic from #14258.

doc/lua_api.md

@@ -5810,6 +5810,8 @@ Utilities
       remove_item_match_meta = true,
       -- The HTTP API supports the HEAD and PATCH methods (5.12.0)
       httpfetch_additional_methods = true,
+      -- Registered and named ABM can be changed on fly (5.13.0)
+      abm_changeable = true,
   }
   ```
 
@@ -6034,6 +6036,9 @@ Call these functions only at load time!
       according to its nature (e.g. `core.registered_nodes`)
 * `core.register_entity(name, entity definition)`
 * `core.register_abm(abm definition)`
+* `core.override_abm(name, new_values)`
+    * Change registered ABM
+    * Only on fields mentonied as changeable can be changed.
 * `core.register_lbm(lbm definition)`
 * `core.register_alias(alias, original_name)`
     * Also use this to set the 'mapgen aliases' needed in a game for the core
@@ -9587,6 +9592,10 @@ in active mapblocks.
 
 ```lua
 {
+    name = "".
+    -- Optional name of ABM.
+    -- ABM with name can be changed at runtime (See `core.override_abm`).
+
     label = "Lava cooling",
     -- Descriptive label for profiling purposes (optional).
     -- Definitions with identical labels will be listed as one.
@@ -9608,14 +9617,18 @@ in active mapblocks.
 
     interval = 10.0,
     -- Operation interval in seconds
+    -- This value can be changed by `core.override_abm` call.
 
     chance = 50,
     -- Probability of triggering `action` per-node per-interval is 1.0 / chance (integers only)
+    -- This value can be changed by `core.override_abm` call.
+    -- If chance is set to 0, ABM is disabled.
 
     min_y = -32768,
     max_y = 32767,
     -- min and max height levels where ABM will be processed (inclusive)
     -- can be used to reduce CPU usage
+    -- This value can be changed by `core.override_abm` call.
 
     catch_up = true,
     -- If true, catch-up behavior is enabled: The `chance` value is
@@ -9631,6 +9644,7 @@ in active mapblocks.
     -- mapblock plus all 26 neighboring mapblocks. If any neighboring
     -- mapblocks are unloaded an estimate is calculated for them based on
     -- loaded mapblocks.
+    -- This function can be changed by `core.override_abm` call.
 }
 ```