You can use type-ahead and fuzzy search in F4 help in custom ABAP code. Type-ahead will work with any database. Fuzzy search only with a HANA database.
First we create a simple test table and fill it with some dummy entries:
Set up Search Help
In SE11 now create elementary search help:
Fill the search help reference to the table and mark the Autosuggest (type-ahead) and mark the full text search:
The fuzzy value of 0,8 allows a similar keyword with a typo to popup. 0,9 be more strict, 0,7 will be less strict. You have to play around. 0,8 is a decent value.
Now you can test with this test program:
PARAMETERS P_TEST type ZTEST-TEXT MATCHCODE OBJECT Z_TEST_FUZZY.
The parameter defined is referring to the search help (matchcode is the old term) we just defined.
Result: if the user starts to key, it will already suggest values:
System wide setup
If it is not working, check with transaction SDSH_CONFIG if the system wide setup is activated or not: