Omniscope doesn't yet support taxonomy filters directly but these can be created using formulas.

Let's say you have several text fields containing free text which you want to search for a number of predefined keywords. You want a checkbox to appear in the filters for each keyword, as follows:

Data table:

ID | DESCRIPTION
1 | Some text including eggs
2 | Some other text including eggs and bacon
3 | Some text including bread

In this case, you might be interested in the keywords "Eggs", "Bacon" and "Bread".

Filter desired:

TAXONOMY
[tick] Eggs (2)
[tick] Bacon (1)
[tick] Bread (1)

Isolating "Eggs" will result in records 1 and 2, since they both contain those keywords.

INSTRUCTIONS TO SET THIS UP

In Omniscope 2.5, choose Data menu > Formulas > Add formula field.
Enter "Taxonomy" as the field name.
Copy and paste the following formula exactly, then carefully customise it (being careful not to miss out a comma) as needed to match your keywords:

IF( SEARCH("eggs", [Description]) > 0, "Eggs,", "")
+
IF( SEARCH("bacon", [Description]) > 0, "Bacon,", "")
+
IF( SEARCH("bread", [Description]) > 0, "Bread,", "")

If you have more than one field, change [Description] to [Field1]+[Field2].

Finally, open Data menu > Manage fields, and find Taxonomy. Ensure the data type is Category (if not, convert), and choose Options > Tokenized. You will be prompted for the token separator character; leave as a comma, unless you have customised it in the formula.
This should result in a filter as described.